In order to meet demands for noise reduction and vibration reduction in an alternating current motor, armature windings are such that two differing three-phase windings are wound by being multiplexed at a predetermined slot pitch, thereby obtaining a multiplex multi-phase winding alternating current motor, and torque pulsation is reduced fey energizing at a phase difference angle corresponding to the slot pitch, whereby a reduction of motor vibration and noise is carried out.
A power converting device that supplies power to the multiplexed multi-phase winding alternating current motor is such that a desired output voltage or a desired current is supplied using PWM (pulse width modulation) control.
For example, PWM control shown in Patent Document 1 is such that a multiple of power converters that supply power to each phase winding and a multiple of PWM control units that control the power converters are included, and PWM control is carried out so that, each PWM control unit executes a switching sequence such that a state wherein a power supply voltage is applied across the phase winding relating to the corresponding power converter, and a state wherein both ends of the phase winding are of the same potential and counter electromotive force of the winding is caused to reflux, can be adopted.
In particular, in order to reduce a ripple in current supplied to the alternating current motor, it is proposed that a phasal relationship of the switching sequences of the multiple of PWM control units is set so that a state wherein the counter electromotive force of each phase winding is caused to reflux does not occur immediately after a state wherein a voltage is applied to all of the phase windings, and a state wherein a voltage is applied to all of the phase windings does not occur immediately after a state wherein counter electromotive force is caused to reflux into all of the phase windings, in one switching cycle.
PWM control means shown in Patent Document 1 is configured so that a value of current flowing through the corresponding phase winding is detected, a deviation from a current command value is calculated, and a switching element is controlled based on a comparison of the deviation and a reference triangular wave. Further, a resistor is provided in order to detect current flowing through the switching element. However, there is no specific description of the resistor that detects the current.
In order to reduce size and weight of a power converting device, it is necessary to reduce the size and weight of each component, or to reduce the number of the component. Therefore, considering reduction of current detecting means as a precondition, a method of computing a duty command value whereby a shunt resistor for detecting current is connected to a direct current portion between a power converter and a direct current power supply negative side, a PWM control unit controls so that an effective voltage vector section in a first-half period and a second-half period in a predetermined multiple of cycles of a PWM signal is of a predetermined period or longer, a aero voltage vector section is equal to or greater than a minimum time determined from a short-circuit prevention period, and the zero voltage vector section is included in at least one of the first-half period and the second-half period, is disclosed in Patent Document 2.